The field of this invention relates to sucker rod pumping wells. When the tubing string of such wells is being pulled for inspection, repair or replacement, fluid contained within the tubing is raised and as each section of the tubing string is disconnected, the fluid spills out creating a working and fire hazard. Means can be provided at the well head to capture the fluid as each section of tubing is pulled, however, this operation is tedious and materially slows the pulling of the tubing string.
Prior inventions have attempted to circumvent this problem, but have been only partially successful due to a variety of drawbacks. One problem has been providing adequate flow area, particularly if the fluid is highly viscous. One line of inventions, of which Marathe, U.S.Pat. No. 3,981,360 is representative, utilized a piston sleeve which was activated by hydraulic pressure to shear a retainer pin thereby opening the tubing ports. The drawback of this invention is that there is no way of closing the port once opened without pulling the entire tubing string and replacing the shear pins. Lewis, U.S. Pat. No. 3,610,337, attempted to solve this problem by means of telescoping members disposed in the tubing string which could be selectively raised or lowered to open or close outlet ports. The main drawback of this invention was its complexity of operation, requiring both a pulling and rotating movement to open the ports and move a spring loaded dog along a complicated path to hold the apparatus in either the open or closed position. Moreover, the portion of the tubing string below the apparatus had to be securely anchored before the apparatus was operable. Thus, a tubing anchor resistive to both rotational and vertical forces was required.
The present invention solves these problems by providing mechanical means to selectively open and close the drain ports. The mechanical means involves a simple rotational movement of the tubing string, the sleeve being held immobile against the well casing, but no anchoring with respect to vertical forces is necessary, and in fact the present device may be moved vertically in the casing without appreciable resistance.